Lecture 11 and 12 Notes
Lecture 11 and 12 Notes 81463 - BIOL 3030 - 001
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This 11 page Class Notes was uploaded by Abigail Towe on Sunday October 4, 2015. The Class Notes belongs to 81463 - BIOL 3030 - 001 at Clemson University taught by Richard W. Blob in Fall 2015. Since its upload, it has received 32 views. For similar materials see Vertebrate Biology in Biological Sciences at Clemson University.
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Date Created: 10/04/15
Tetra od Ori ins 0 Review 0 air is less dense and much less viscous than water 0 on land the skeleton now has to support the body weight 0 feeding chances suction feeding no longer works for the animal doesn t work on land 0 for acquiring oxygen gills are no longer viableeffective I but since air is easy to move breathing will work with lungs and it s cheapeasylittle cost 0 even though lungs weren t evolved for that remember lungs were already there in aquatic animals loss of electrical and lateral line sensory system on land air temperatures are less stable than temperatures in water risk of drying out on land because water doesn t surround you anymore Tetrapod Relationships with Sarcopterygians 0 Remember Sarcopterygians are osteichthyans that have robust bony skeleton in appendages fins or limbs 0 within sarcopterygians tetrapods appear o Tetrapods are sarcopterygians with 4 feet 0 feet fingerstoes not fins 0 Tetrapodomorpha gt united by sharing choanae internal nostril o the choanae allows air to pass through external nostrils to lungs with mouth closed 0 the animal can stay in shallow water but bring nose out of water to breathe therefore they can stay in water to sneak Fossil Relatives of Early Tetrapods Devonian o First look at the Eustenopterm osteolepiform o This fish has a choana and has some bones in the fins but still a fish Panderichthys elpistostege o lose dorsal and anal fins flat body 0 forefin closer to tetrapod limb than hindfin this is mosaic evolution o Early tetrapod Acanthostega o Dactylus limbs limbs with digits 0 but no robust skeleton The head and body profile chances to become more flat The dorsal and anal fins are lost The fore and hind fins transition into well defined bones to form fingerstoes o the fore fins develop to a tetrapod limbs faster than the hindfin I the fore fin develops a space in between bones like radius and ulna but hind fin doesn39t have this gap in transitional fossils I chances in fore fins occurs much sooner than hind fin makes sense because you are moving yourself with your fore fins 0 mosaic evolution major transitions that happen in particular placestimes and each transition helps to get to tetrapod Tetrapods o Synapomorphy o 4 feet dactylus limbs with fingers and toes o Early tetrapods found in Greenland dated to Late Dovian period 378352 million years ago Acanthostega 0 But Greenland has high contrast of seasons so it doesn t seem like a good home But during the Late Dovian period Greenland was actually close to the equator so the environment would have been more suitable o Other distinctive qualities of tetrapods 1 retain tail fin rays 2 hand and foot polydactylous 7 hind digits 8 fore digits in the early tetrapod Acanthostega a also the digits were not symmetrical no pattern it can range from small large large then small fingers that doesn t look normal 3 Gills a blood vessel grooves on arches o All of this helps tetrapods live nearshoresshallow water This features evolved in water helped them in water Remember the 1st tetrapods were quatic o The are very similar to modern crocodiles flat bodies nostrils and eyes on dorsal side of head Earlv Tetrapods amp Evolution of Development o Polydactyly in fossil taxa 5 digits is not a primitive condition not ancestral for tetrapods o This means that being polydactyly with 7 or 8 digits is ancestral o The transition from 8 to 5 one possible mechanism of this transition is a pattern known as developmental truncation o truncation means cutting it short 0 If development is shortened last features don t appear 0 The order of development of digits is that it starts on one side of the arm the digits develop across the palm of the hand So if the development time chances then less digits are formed Early Tetrapods Chances in Feedinq amp Hearinq o Acanthostega early tetrapod skull o the skull is flat 0 the nose and eyes are on top of skull o This encourages feeding at surfacein shallows So since they are not surrounded by water they cannot use suction feeding anymore They had to rely on ram feeding and biting I So to better use these two mechanisms to eat the bones of the skull will need to be solid fused together and help keep the head stable to help keep the head still as foodprey is attacked important because prey usually movesfights back 0 Hyomandibula bone this is the major bone that changed 0 it used to connect jaw to braincase with mobile joint 0 but now that tetrapod are no longer flaring jaws out for suction the hyomandibula bone chances to adjust to new feeding mechanisms 0 The function of the hyomandibula chances from skull flaring to hearing stapes I stapes bone is smaller than the hyomandibula 0 but it s still a chunky thick bone This prevents being able to vibrate very frequently so it can t hear high pitches So most sounds they would hear would have been low pitched o The hyomandibula bone now connects skull to tympanic membrane eardrum to serve to pass sound waves to brain Early Tetrapods and the Invasion of Land 0 But WHY invade land 0 They didn t HAVE to So why 0 they were well adapted and good at living in water So why 0 Old idea escape drying conditions in water 0 problem with this idea if you look at rock records from Devonian period there is NO record of droughts o New Idea exploration of novel food sources 0 invertebrates already invaded land before tetrapods there was insects on land 0 so tetrapods could have left water for new food sources o Newer New Idea heat up faster 0 moving to land could allow vertebrates to heat up their body temperatures I remember vertebrates rely on outside environment to heat up body water temperatures are stable not always a good thing because if water is cold it will stay cold and vertebrates can t heat up therefore vertebrates could rely on the sun for heating their body sun basking At first they went on land for heat then went back into water and carry the heat back with them But after a while they stopped going back 0 It s possible that both of the new ideas contributed to the reason of why 0 O O O Early Tetrapod Relationships 0 Main points 0 Basal tetrapod diversity I first lineages not a clade I Acanthostega early tetrapod highly aquatic o no robust skeleton larger tail fin ACM HI 93 I Ichthyostega one of the first of which good evidence was found more terrestrial robust ribs and girdle less tail fin but the hearing is still suited for underwater heating the feet are not true feet close to a seal flipper than a foot could be secondarily aquatic the transition was back and forth between water and land recurring theme in early tetrapods to go back to water q r r x I y 41 1 f mf iff Jj a er 5 V39 t amp L a 44 11 A 39 law 7 i l wquot Tii g o batrachromophs vs reptiliomorpha I the difference between these two groups is very close to the different between amphibians vs amniotes I batrachomorphs most taxa thought of as amphibians o distinguished by 0 flat skull o no kinesis o 4 or fewer fingers on hand I one taxa of batrachomorphs lepospondyls diverse small taxa I One example Nectrideans found in Texas dated from Permian period aquatic bizarre horns on skulls of adults head forms into boomerang shape as adult 0 doesn t know what the function of this head shape is I Another example Aistopoda first example of limbless vertebrates operates more like a snake lived on land fossils found in Europe dated back to CarboniferousPermian penod I Temnospondyls from Carboniferous period recent many big terrestrial taxa early but later survivors mainly aquatic grade of taxa from which modern amphibians groups evolved survive Permian period but died out in cRetaceous except for modern groups I Basal reptiliomorpha diversity 0 distinctions deeper skull more terrestrial o example Anthracosaurus carbtrais period 0 large longlimbed 0 example Diadectomorpha permian o Herbivorous among first tetrapods to feed this way during this time most were carnivorous o prebatrachomorph diversity I looking at the diversity before the batrachomorphs I the book groups all these species together in lepospondyls o representative temnospondyls and origin of modern amphibia lissamphibia Paleozoic World A completely different place o The continents were converged into pangea almost all terrestrial exposed land would have been together in continuum there were 10s of millions of years of this supercontinent pangaea However no flowering plants There was giant seed ferns giant horsetails giant club mosses There were higher levels of oxygen These unusual high oxygen levels made it possible to have giant insects dragonflies 3 feet long 0 But at least half of all of this was removed with the major vertebrate extinction at the end of the Permian period 12 of all tetrapods died 0 Extinction because massive volcanic eruptions in Siberia release lava and greenhouse gases raise water temperatures to 6 degrees Celsius I This disrupted ocean circulation and climate and air flow Amphibians and mammallike reptiles took biggest hits past disasters help shape present diversity What we see today is the groups that made it through this disaster Amphibian Diversity Review 0 temnospondyls from where modern amphibians are derived 0 so no we are not temnospondyls o earliest tetrapods lived in aquatic environments 0 then eventually moved to land 0 tetrapods split into two major clades batrachomorpha and reptiliomorpha o a group under batrachomorpha called lissamphibia lead to modern amphibians o batramorpha o caecilians clade gymnophiona I no limbs o salamanders clade urodela I yes limbs o frogs clade anura I yes limbs and specialized jumpers Lissamphibia Svnapomorphies 1 skin smooth glandular a highly permeable to gas and water i oxygen exchange but also exchanges of water b two types of glands i mucus glands secrete mucus 1 the mucus keeps animal moist to prevent water loss prevent evaporation and a predator defense because if prey is slippery it helps it escape or avoid being eaten by predator ii poison glands 1 located all throughout the skin 2 secretes poison chemicals 3 not all poisons are deadly various toxicities a potential to kill or cause hallucinations c no armor i we can tell that the skin of these amphibians are different from reptiliomorpha because these lissamphibians do not have armor d amphibians shed their skin regularly i the stratum corneum layer comes off 1 this layer is less permeable ii skin sloths off 2 has pedicellate teeth a these teeth are bicuspid has two cuspids b pedicel the distinct region where the crown of the tooth is connected to the jaw c this classifies them as predators because these teeth help to kill other animals for food d exception some frog tadpoles do it plant material but by the time they metamorphosize into their adult size they are predators Lissamphibians Bimodal life history and the exceptions o fertilized egg gt aquatic tadpole gt undergoes metamorphosis dramatic reorganization of body systems gt changes into much more terrestrial inhabiting adult therefore they are considered to have a double life because aquatic than terrestrial life excep ons 0 direct development I tadpoles are kept in a sac but on land and when they hatch they are already in their terrestrial state live on land I paedomorphosis exhibit juvenile features o examples mudpuppy salamander o sexually mature mudpuppies have gills which are juvenile features fossil record of lissamphibians o caecilians Jurassic period 0 known from Arizona 0 distinguished by mode of locomotion limbless 0 but caecilians have tiny limbs o salamander mid Jurassic 0 actually show outlines of soft tissues features that usually aren t preserved and you can see gills o Frogs Triassic o anura literally means no tail amphibians Caecilians Clade Gymnophiona about 200 species fossil record Jurassic today they live in tropics limbless under a foot long 0 but one single species are 15 meters 0 specialized for burrowing 0 they look like a worm and because no limbs they use their head to burrow 0 therefore their skull is highly ossified solid bone skull o if you re burrowing in soil then you eat food in soil such as earthworms and bugs so they also has jaws high bite forces for their body size 0 also because of underground lifestyle 0 reduced eyes or no eyes 0 therefore they rely on smell has chemosensory organ tentacle I they have two tentacles one on each side of head I between the nostrils where eyes would be I the muscles that control these tentacles are the muscles that used to control the eyes 0 eye muscles greatest conservation of muscles same muscles throughout many life forms 0 but caecilians are the exception because they are more than the standard 6 muscles 0 to burrow they use their head plus curvature in their spine 0 curvature allowed with loose skin 0 curves spine then springs itself forward has terminal anus loss or reduction of left lung external evidence of segments annuli o sometimes marked by presence of dermal scales 0 has a large range of reproductive habitslifestyles 0 females can guardwrap around eggs to protect o or livebearing where they remain inside mother while growing I they eat the uterine lining as they grow Salamanders and Frog 0 Clade Batrachia o salamanders and frogs are sister taxa 0 they are considered together because they share the distinct anatomical structure called the opercular apparatus o Synapomorphy shared opercular apparatus 0 different from the feature that is in ratfish more complicated than in fish 0 it s a collection of structures that together connects the ear region to their shoulder girdle I connected by muscle operculum and columella o columella stapes inner ear bone 0 the advantage of this system transfers sound up from feet to the structure in ear so that they can now detect groundborne vibrations along with sound like usual I since these animals are low and on the ground it helps them hear and feel when predator is coming 0 Salamander Synapomorphy 0 development traits Salamanders are recognized by long tail primitive but NOT a synapomorphy because everything had a tail Frog Synapomorphy o saltatory locomotion jumping Salamander Diversity Northern Hemisphere don t have to memorize branching pattern just recognize the diversity and changes basal group Sirens o can slither around on land but mostly highly aquatic o lose hindlimbs 0 small forearm next Cryptobranchus 0 one species called hellbender lives in mountains of North CArolina 0 about 3 feet 0 but in Japan 5 feet in length 0 still aquatic next branch off is sister taxa columbidae and plethodondriate 0 even smaller forearms and hind legs 0 but they do keep all 4 of them 0 plethodontids make up 13 of total I key features lungless 0 uses cutaneous respiration I terrestrial because a more ready source of oxygen for this respiration system is advantageous remember limb loss is independent for each species ancestrally salamanders have 4 limbs proteidae mudpuppies salamandridae newts ambystomatidae tiger salamander allies Frog Diversity Pipids o totally aquatic swimmers 0 flat body Bufonidae 0 true toads o toads are a group within frogs o toad short legs so it39s specialized for hopping short jumps I warty skin I toxins released from behind eyes I more terrestrial form of frogs o Hylids o treefrogs 0 generally smaller in body size 0 long skinny legs great jumpers o Dendrobatids o poison dart frogs I because they eat certain insects ants gets toxins from ants stores the toxins and then uses them to protect themselves I they can eat nontoxic ants and lose toxicity 0 small body size 0 tropical o Ranids o bullfrogs o jumpers I water frogs jumps in shallow water Amphibian Musculoskeletal Function Salamanders 0 so whereas fish just have head and vertebrate no neck salamanders have neck 0 salamanders have regional specialization of vertebral column to allow neck 0 the atlas cervical is the structure that forms neck 0 also because of the regional specialization 0 they have trunk with ribs 0 scarum that is fused to hip girdle o casuals tail 0 because of the regional specialization it allowed the locomotion to change to lateral bending during walking side to side walking gt this increases stride length faster locomotion o the lateral bending of body helps them walk since their body type has limbs that are in a sprawling posture o lateral bending allows them to walk without having to change their posture Amphibian Musculoskeletal Function Frogs o the trunk becomes longer and stiffer gt prevents axial movement shortening and development of urostyle tibia and fibula are fused together and elongated ankle bones are lengthened shorter forelimbs but longer hind limbs that are highly muscled aids in high power production for jumping o with various body shapes frogs jumping chances 0 long hind limbs but short forelimbs swimmers 0 long hind limbs and long forelimbs jumpers 0 short hindlimbs but long forelimbs hoppers 0 short hind limbs and short forelimbs burrowers o webbing between toes helps in gliding to have a more gentlegraceful landing flying frog Amphibian Musculoskeletal Function Locomotion o Arboreal species 0 has toe pads that secrete mucus to aid in adhering to surfaces by surface tension I there are glandular disks at toe tops to aid in grasping o intercalary bones I helps set tip of the toe to set it further away from digit to allow more surface contact to help it stick to the surface 0 if they don t have toe pads or intercalary bones frog can have recurved spatulate terminal phalanx I the distal end of the toe phalanx can curve so that it can have a greater force to stick onto surface by increasing surface area o example green salamander o tongue protrusion o tongue flips from bottom side in mouth tongue is attached at front of jaw 0 common in frogs I but pepids do not use this underwater I but those on land do use this method 0 plethodontidae lungless lineage I best developed tongue flip I can shoot out the length of body or more I achieved by loss of lung mouth no longer related to breathing so it can specialize for feeding behaviors 0 so loss of lung could allow specialize for feeding to occur because no trade off more energy devoted to feeding
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